FAILED: patch "[PATCH] io_uring: disallow self-propelled ring polling" failed to apply to 5.15-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 5.15-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

Possible dependencies:

7fdbc5f014c3 ("io_uring: disallow self-propelled ring polling")
2ba69707d915 ("io_uring: clean up io_poll_check_events return values")
d245bca6375b ("io_uring: don't expose io_fill_cqe_aux()")
f3b44f92e59a ("io_uring: move read/write related opcodes to its own file")
c98817e6cd44 ("io_uring: move remaining file table manipulation to filetable.c")
735729844819 ("io_uring: move rsrc related data, core, and commands")
3b77495a9723 ("io_uring: split provided buffers handling into its own file")
7aaff708a768 ("io_uring: move cancelation into its own file")
329061d3e2f9 ("io_uring: move poll handling into its own file")
cfd22e6b3319 ("io_uring: add opcode name to io_op_defs")
92ac8beaea1f ("io_uring: include and forward-declaration sanitation")
c9f06aa7de15 ("io_uring: move io_uring_task (tctx) helpers into its own file")
a4ad4f748ea9 ("io_uring: move fdinfo helpers to its own file")
e5550a1447bf ("io_uring: use io_is_uring_fops() consistently")
17437f311490 ("io_uring: move SQPOLL related handling into its own file")
59915143e89f ("io_uring: move timeout opcodes and handling into its own file")
e418bbc97bff ("io_uring: move our reference counting into a header")
36404b09aa60 ("io_uring: move msg_ring into its own file")
f9ead18c1058 ("io_uring: split network related opcodes into its own file")
e0da14def1ee ("io_uring: move statx handling to its own file")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 7fdbc5f014c3f71bc44673a2d6c5bb2d12d45f25 Mon Sep 17 00:00:00 2001
From: Pavel Begunkov <asml.silence@gmail.com>
Date: Fri, 18 Nov 2022 15:41:41 +0000
Subject: [PATCH] io_uring: disallow self-propelled ring polling

When we post a CQE we wake all ring pollers as it normally should be.
However, if a CQE was generated by a multishot poll request targeting
its own ring, it'll wake that request up, which will make it to post
a new CQE, which will wake the request and so on until it exhausts all
CQ entries.

Don't allow multishot polling io_uring files but downgrade them to
oneshots, which was always stated as a correct behaviour that the
userspace should check for.

Cc: stable@vger.kernel.org
Fixes: aa43477b04025 ("io_uring: poll rework")
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/3124038c0e7474d427538c2d915335ec28c92d21.1668785722.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/io_uring/poll.c b/io_uring/poll.c
index c34019b18211..055632e9092a 100644
--- a/io_uring/poll.c
+++ b/io_uring/poll.c
@@ -246,6 +246,8 @@ static int io_poll_check_events(struct io_kiocb *req, bool *locked)
 			continue;
 		if (req->apoll_events & EPOLLONESHOT)
 			return IOU_POLL_DONE;
+		if (io_is_uring_fops(req->file))
+			return IOU_POLL_DONE;
 
 		/* multishot, just fill a CQE and proceed */
 		if (!(req->flags & REQ_F_APOLL_MULTISHOT)) {